Do new guidelines enable a more accurate comparison of [18F]FDG PET/CT features with histopathology in primary breast cancer?

Recent EANM–SNMMI guidelines suggest that quantitative [ 18 F]FDG PET parameters, including standardised uptake values (SUV), metabolic tumour volume (MTV) and total lesion glycolysis (TLG), provide valuable prognostic information in breast cancer. We aim to evaluate the association between [ 18 F]FDG PET parameters in a large real-world cohort of high-risk breast cancer patients and the four main intrinsic subtypes of breast cancer defined by the EANM–SNMMI guidelines. All women with newly diagnosed high-risk breast cancer undergoing [ 18 F]FDG PET/CT between 1/8/22 and 17/4/2025 were eligible for inclusion. Primary tumour metabolic parameters (SUV max/mean/peak , SUV heterogeneity index (HI), MTV, TLG) were measured and compared with histological grade, hormone receptor status (oestrogen receptor (ER), progesterone receptor (PR)) and Human Epidermal Growth Factor Receptor 2 (HER2) expression. Cases were classified according to EANM–SNMMI histological groupings: Group 1 (G1) representing Luminal A-like (HR+ /HER2− and low-grade/low proliferation), Group 2 (G2) Luminal B-like (HR+ /HER2− and high-grade/high proliferation), Group 3 (G3) HER2+ (HR + or −) lesions, and Group 4 (G4) triple negative breast cancer (TNBC). Hormone receptor status was analysed separately. 185 cases were included for analysis: G1 ( n = 48), G2 ( n = 35), G3 ( n = 54) and G4 ( n = 48). Significant differences were observed between groups for SUV max , SUV mean , SUV HI and MTV; post hoc analysis revealed TNBC, HER2 + and Luminal B tumours exhibited significantly higher SUV max than Luminal A cancers, with significantly higher SUV mean and SUV peak in TNBC and Luminal B versus Luminal A. The SUV HI showed significantly lower heterogeneity in the Luminal A group compared with Luminal B ( p = 0.02) and HER2-positive tumours ( p = 0.03), with no other significant pairwise differences. When looking at MTV, only the Luminal A vs. Luminal B comparison reached significance, with larger MTVs observed in Luminal B tumours. ER + and PR+ tumours showed significantly lower SUV parameters ( p < 0.05) when compared with receptor-negative tumours, but no significant differences were observed for volumetric parameters (MTV and TLG) ( p > 0.05). HER2 scores (negative/low/positive) showed no significant association with SUV or volumetric PET parameters. In our large real-world cohort of high-risk breast cancer patients, quantitative [¹⁸F]FDG PET parameters demonstrate significant associations with the histopathological breast cancer subtypes recommended in the EANM–SNMMI guidelines.